Implantable medical lead with threaded fixation

Abstract

The disclosure is directed to securing electrodes of a medical lead adjacent to a target tissue site. The medical lead may include one or more threaded fixation structures disposed circumferentially about the outer surface of the lead body, or elongated member, that resembles a “screw” or “auger.” During implantation, a clinician may rotate the entire lead to “screw” the lead into the tissue of the patient until electrodes of the lead reside adjacent to a target tissue. In this manner, the threaded fixation structure secures the lead within the patient to resist lead migration and improper therapy and provide a fine adjustment for depth of placement. The threaded fixation structure may be disposed on a portion of the lead proximal to or distal to the electrodes of the lead or over the portion of the lead that includes the electrodes.

The invention claimed is: 
     
       1. A medical lead for treating incontinence, the medical lead comprising:
 an elongated member having a proximal end and a distal end, the proximal end being configured to electrically and mechanically couple to a medical device comprising stimulation circuitry; 
 four stimulation electrodes configured to deliver electrical stimulation generated by the medical device to a sacral nerve of a patient when the elongated member is electrically and mechanically coupled to the medical device; 
 a plurality of fixation structures arranged to form a helical pattern around a portion of an outer surface of the elongated member and configured to engage tissue within the patient, wherein the helical pattern is proximal of the four electrodes, and wherein each fixation structure of the plurality of fixation structures has a free end configured to be spaced from the elongated member; and 
 a sheath configured to cover at least the portion of the outer surface of the elongated member including the plurality of fixation structures, wherein the plurality of fixation structures is configured to fold towards the elongated member when restrained by the sheath, and wherein the free end of each fixation structure of the plurality of fixation structures is configured to be deployed as the sheath is removed from the plurality of fixation structures to anchor the lead. 
 
     
     
       2. The medical lead of  claim 1 , wherein the plurality of fixation structures is disposed proximal of all stimulation electrodes disposed along the elongated member, the all stimulation electrodes comprising the four stimulation electrodes. 
     
     
       3. The medical lead of  claim 1 , wherein each fixation structure of the plurality of fixation structures comprises, opposite of the free end, a secured end attached to the elongated member. 
     
     
       4. The medical lead of  claim 1 , wherein the sheath is configured to collapse the plurality of fixation structures to reduce a diameter of the medical lead until the sheath is removed from the plurality of fixation structures. 
     
     
       5. The medical lead of  claim 1 , wherein the plurality of fixation structures is a first plurality of fixation structures and the helical pattern is a first helical pattern, further comprising a second plurality of fixation structures arranged to form a second helical pattern and disposed distal of the four electrodes. 
     
     
       6. The medical lead of  claim 1 , wherein the plurality of fixation structures comprise polyurethane. 
     
     
       7. The medical lead of  claim 1 , wherein each fixation structure of the plurality of fixation structures have a height between 0.1 mm and 3 mm from an outer surface of the elongated member. 
     
     
       8. The medical lead of  claim 1 , wherein each stimulation electrode of the four stimulation electrodes comprises a ring electrode disposed at a respective location along the outer surface of the elongated member. 
     
     
       9. The medical lead of  claim 1 , wherein the plurality of fixation structures is configured to fold towards the distal end of the elongated member when restrained by the sheath. 
     
     
       10. The medical lead of  claim 1 , wherein the plurality of fixation structures are configured to fold towards the proximal end of the elongated member when restrained by the sheath. 
     
     
       11. The medical lead of  claim 1 , wherein the plurality of fixation structures are configured to extend away from the elongated member in response to removal of the sheath. 
     
     
       12. The medical lead of  claim 1 , wherein the elongated member defines an outside diameter between 0.5 mm and 5 mm. 
     
     
       13. A method for treating incontinence, the method comprising:
 inserting a medical lead to a location proximate to a sacral nerve of a patient, wherein the medical lead comprises:
 an elongated member having a proximal end and a distal end, the proximal end being configured to electrically couple to a medical device comprising a stimulation circuitry; 
 four stimulation electrodes disposed closer to the distal end of the elongated member than the proximal end of the elongated member, the four stimulation electrodes being configured to deliver electrical stimulation generated by the medical device to the sacral nerve of the patient when the elongated member is electrically and mechanically coupled to the medical device; and 
 a plurality of fixation structures arranged to form a helical pattern around a portion of an outer surface of the elongated member and configured to engage tissue within the patient, wherein the helical pattern is disposed proximal of the four stimulation electrodes disposed along the elongated member; 
 
 removing a sheath from the medical lead to deploy the plurality of fixation structures as the sheath is removed from the plurality of fixation structures to anchor the lead in tissue of the patient, wherein the sheath is configured to deflect and cover the plurality of fixation structures, and wherein the plurality of fixation structures are configured to fold towards the elongated member when restrained by the sheath; and 
 attaching the medical lead to the medical device. 
 
     
     
       14. The method of  claim 13 , wherein inserting the medical lead comprises rotating the medical lead. 
     
     
       15. The method of  claim 13 , wherein removing the sheath from the medical lead comprises withdrawing the sheath from the medical lead to deploy the plurality of fixation structures as the sheath is withdrawn from the plurality of fixation structures to anchor the lead in the tissue of the patient. 
     
     
       16. The method of  claim 13 , wherein the plurality of fixation structures is attached to the elongated member. 
     
     
       17. The method of  claim 13 , wherein the plurality of fixation structures comprises a polymer. 
     
     
       18. A system for treating incontinence, the system comprising:
 a medical lead comprising:
 an elongated member having a proximal end portion with a plurality of electrical contacts and a distal end, the elongated member defining a central axis; 
 four stimulation electrodes configured to deliver electrical stimulation generated by a medical device to a sacral nerve of a patient, the four stimulation electrodes being equally spaced along the central axis; 
 a plurality of conductor wires between the four electrodes and the plurality of electrical contacts; 
 a plurality of polymer fixation structures arranged in a helical pattern around a portion of the elongated member and configured to engage tissue within the patient, each fixation structure of the plurality of polymer fixation structures having a free end, each fixation structure of the plurality of polymer fixation structures having a deployed height between 0.1 mm and 3 mm from an outer surface of the elongated member to the free end, wherein the helical pattern is proximal from the four stimulation electrodes; 
 a visual marker associated with the medical lead; 
 
 a sheath configured to cover at least the plurality of polymer fixation structures, wherein the plurality of polymer fixation structures are configured to fold towards the elongated member when restrained by the sheath, and wherein the plurality of polymer fixation structures are configured to be deployed as the sheath is removed from the plurality of fixation structures to anchor the lead; 
 a stimulator having a rechargeable battery, the stimulator being configured to deliver electrical stimulation therapy to the sacral nerve of the patient via at least one electrode of the four stimulation electrodes of the medical lead within the patient, the proximal end portion of the elongated member being configured to mechanically couple to the stimulator; 
 a clinician programmer configured to program stimulation therapy for the patient; and 
 a patient device configured to control stimulation therapy from the stimulator. 
 
     
     
       19. The system of  claim 18 , wherein each stimulation electrode of the four stimulation electrodes comprises a cylindrical stimulation electrode. 
     
     
       20. The system of  claim 18 , wherein the plurality of fixation structures is constructed from polyurethane and configured to fold towards the proximal end of the elongated member when restrained by the sheath. 
     
     
       21. The system of  claim 18 , wherein the plurality of fixation structures is configured to extend away from the elongated member in response to removal of the sheath. 
     
     
       22. A medical lead for treating incontinence, the medical lead comprising:
 an elongated member having a proximal end and a distal end, the proximal end having four electrical contacts, the electrical contacts being configured to electrically couple the medical lead to a medical device comprising stimulation circuitry; 
 four stimulation electrodes disposed closer to the distal end of the elongated member than the proximal end of the elongated member, the four stimulation electrodes being configured to deliver electrical stimulation generated by the medical device to a sacral nerve of a patient when the elongated member is electrically and mechanically coupled to the medical device; 
 a plurality of discontinuous fixation structures disposed in a helical shape around a portion of an outer surface of the elongated member and configured to engage tissue within the patient, wherein the helical shape is proximal from the four electrodes, and wherein each fixation structure of the plurality of discontinuous fixation structures has a free end configured to be spaced from the elongated member; and 
 a sheath configured to cover at least the portion of the outer surface of the elongated member including the helical shape, wherein the plurality of discontinuous fixation structures are configured to fold towards the elongated member when restrained by the sheath, and wherein the plurality of discontinuous fixation structures are configured to be deployed as the sheath is removed from the plurality of fixation structures to anchor the lead.